Is the CPR overflow for the 75 or for the twenty?
It's for the 75.
Does the 75 have a built in internal overflow?
No
This was the same setup that was used by the guys at Premium Aquatics on their reef tank.
I was going to set the 20 below the 75 but i think that i am going to put it at the...
I don't have it set up yet, but i have a 20g aquarium, CPR CS90 overflow, mag drive utility pump and an Aqua lifter vacuum pump. I want to connect this to my new 75g setup.